Optimization of Abrasive Water Jet Cutting of Ductile Materials

Full factorial design of experiments was developed in order to investigate the effects of jet pressure, abrasive mixing rate, cutting feed, and plate thickness upon three response variables, surface finish of cutting wear zone, percentage proportion of striation free area, and maximum width of cut. The set of sixteen experiments was performed on each of the following two ductile materials： AISI 4340 （high strength low alloy steel, hardened to 49HRc） and Aluminum 2219. Analysis of Variance （ANOVA） was performed on experimental data in order to determine the significance of effects of different parameters on the performance measures. It was found that cutting feed and thickness were highly influential parameters, while abrasive mixing rate is influential upon surface roughness only. Strong interaction was found between jet pressure and workpiece material. Multi-criteria numerical optimization was performed in order to simultaneously maximize/minimize different combinations of performance measures.

Numerical Simulation Research of Liquid-Solid Two-Phase Flow in Abrasive Water Jet Nozzle

According to the Lagrange discrete phase model of multiphase flow, mathematical model of the abrasive water-jet （AWJ） nozzle based on the multi-phase movement was introduced, then the boundary conditions was determined and the liquid-solid turbulence which is isothermal, can not be compressed and steadystate in the cone-cylinder nozzles of the export of the pre-mixed AWJ was simulated applying the software FLUENT. The results showed that： the axial velocity and dynamic pressure of the continuous phase in the nozzle were axial symmetry notable, and at the axis had a extreme point; abrasive accelerated at two points, in front contractive segment, the rate increased rapidly, and in the back straight one, the speed accelerated slowly. The length of the cylinder is 100 mm, the diameter of the nozzle is 8 mm, and the angle of the cone is 15°. There is a extreme point of the rate at the point 10 mm in the established model. The results of simulation laid the foundation for optimizing the nozzle structure, improving efficiency and developing the nozzle.

Air flow exploration of abrasive feed tube

An abrasive water-jet cutting process is one in which water pressure is raised to a very high pressure and forced through a very small orifice to form a very thin high speed jet beam. This thin jet beam is then directed through a chamber and then fed into a secondary nozzle, or mixing tube. During this process, a vacuum is generated in the cham- ber, and garnet abrasives and air are pulled into the chamber, through an abrasive feed tube, and mixes with this high speed stream of water. Because of the restrictions introduced by the abrasive feed tube geometry, a vacuum gradient is generated along the tube. Although this phenomenon has been recog- nized and utilized as a way to monitor nozzle condition and abrasive flowing conditions, yet, until now, conditions inside the abrasive feed line have not been completely understood. A possible reason is that conditions inside the abrasive feed line are complicated. Not only compressible flow but also multi- phase, multi-component flow has been involved in inside of abrasive feed tube. This paper explored various aspects of the vacuum creation process in both the mixing chamber and the abrasive feed tube. Based on an experimental exploration, an analytical framework is presented to allow theoretical calculations of vacuum conditions in the abrasive feed tube.